Amphibians are a bellweather species. Much like a canary in a coal mine they indicate the overall health of the environment.
When I lived in Bermuda I used to sit and watch the giant toads come out around sunset and snap up the giant cockroaches as they emerged from the septic tank vent pipe. I began to hear about the startling high numbers of these massive amphibians being found with extra legs, even extra heads. There are pesticides for sale in Bermuda which are made in the US but are illegal for use in the US. The pesticides for sale in the US are tested, minimally, for safety as individual chemicals, as if in a vacuum. Nothing in nature occurs in a vacuum. It has been suspected that the naturally resulting cocktail of chemicals derived from our love of poisons is far more dangerous both to the ecosystems upon which we depend and indeed directly upon ourselves than any chemical in isolation. Recent research bears this out. This is over on the Organic Consumers Association website where you will also find a link to the original research.
"PITTSBURGH, Nov. 13 (UPI) -- U.S. scientists studying 10 of the world's most popular approved pesticides say, when combined, the chemicals caused 99 percent mortality in tadpoles.
University of Pittsburgh researchers said the U.S. Environmental Protection Agency-approved pesticides, when mixed together, can decimate amphibian populations even if the concentration of the individual chemicals is within limits considered safe.
Such "cocktails of contaminants" are frequently detected in nature, the scientists said, noting their findings offer the first illustration of how a large mixture of pesticides can adversely impact the environment.
Associate Professor Rick Relyea, the study's lead author, exposed gray tree frog and leopard frog tadpoles to small amounts of the 10 pesticides -- insecticides carbaryl, chlorpyrifos, diazinon, endosulfan, and malathion, as well as five herbicides: acetochlor, atrazine, glyphosate, metolachlor, and 2,4-D.
He used each of the pesticides alone, the insecticides combined, a mix of the five herbicides, or all 10 of the poisons.
Relyea found a mixture of all 10 chemicals killed 99 percent of leopard frog tadpoles, as did the insecticide-only mixture."